Alcohol by volume. This is a measurement of the percent of alcohol present in a volume of liquid. To obtain this number take the original gravity and subtract the final gravity then multiply the answer by 131.25. One pound of fermentable sugar is approximately equal to 1% ABV in a 5 gallon batch. ABV = ABW x 1.25.

Alcohol by weight. This is a measurement of the percent of alcohol present in a volume of liquid. The percent is the number of grams of alcohol in 100 centiliters (e.g. 5%ABW equals 5 grams of alcohol/100 cl) - ABW = ABV x .80

A malt high in the phytase enzyme, which breaks down phytin into phytic acid, thus lowering the mash pH. Typically only used in Germany, where the Reinheitsgebot prevents brewers from using food-grade acids to do the same thing.

A relatively low temperature rest (95F) used to activate the phytase enzyme, the desired result of which is to lower the pH of the mash. This is generally only employed in Germany where the Reinheitsgebot prevents the use of things like acid blend which serve the same purpose. A small amount of acid malt is used.

A substance commonly used to remove both organic and inorgainic contaminants from water. Most water filtration units use activated charcoal. Does not remove all microorganisms (i.e., activated charcoal cannot be used to make unsanitary water safe).

American Homebrewers Association. Non-profit organization which promotes the hobby of homebrewing, and sanctions homebrew competitions. Founded by Charlie Papazian, author of several books on homebrewing.

A small device, designed to be affixed to the top of a fermenter. An airlock allows the CO2 produced during fermentation to escape, without allowing airborne bacteria to enter the fermenter. The most common type is called a three piece airlock, and consists of a small plastic chamber, a float which sits inside the chamber, and a dust cover. The chamber is partially filled with liquid - plain water, sanitizing solution, or vodka, depending on how paranoid you are - and the CO2 bubbles out from underneath the float. There is also a single-piece, "sideways S" type of airlock which is in fairly widespread use.

The measure of the amount of space the alcohol in a beer takes up as a percentage of total volume. This is the worldwide standard for measuring the alcohol content in beer. The United States traditionally used alcohol by weight (ABW) to measure alcohol content, but more and more American brewers are now adopting ABV.

The measure of the weight of alcohol as a percentage of total weight of the liquid. This standard is being used much less frequently nowadays. To convert ABW to ABV, multiply the ABW x 1.25. Conversely, to get the ABW from ABV multiply the ABV x 0.8.

Alcohol content is measured in percent. The percentage may be either by volume or weight. Since alcohol is lighter than water, the %volume number is larger than the %weight number by a factor of 1.25. Beer in the US is commonly measured in %weight (e.g., 3.2% beer has at most 3.2% by weight of alcohol, or 4% by volume).

Brewers yeast which typically works at temperatures of 60F and above, scientific classification Saccharomyces cerevisiae. Some (but not all) ale yeasts are top cropping - that is, they tend to float, and collect on the surface of the beer as fermentation progresses.

A method of brewing where pre-made malt extract powders or syrups are not used. All of the fermentable sugars are obtained by mashing malt, and (possibly) other grain adjuncts. All-grain brewing requires more equipment, and is more time-consuming than extract brewing, but gives you a great deal more control over the final product. As a rough analogy, think of the difference between baking a cake from a boxed cake mix, versus baking a cake from scratch.

A resin contained in the hop plant that is responsible for the bitterness in beer. When purchasing hops, the alpha acid content of the hops will be given as a percentage and printed on the package cover.

A method used for specifying the quantity of bittering hops, commonly used in homebrew recipes; commonly abbreviated as AAU, and also referred to by some authors as Homebrew Bitterness Units, or HBUs. One AAU is equivalent to one ounce of hops with an alpha acid rating of 1%. Example: If a recipe calls for 10 AAUs of bittering hops, and your hops have a rating of 5%, you need two ounces. (AAUs are the same as HBUs.)

One of the two primary enzymes responsible for breaking starch down into sugar. Alpha amylase is most active in the upper range of mashing temperatures (155F-160F) and is responsible for producing higher-order (larger) sugars which are less fermentable, producing a beer with more body.

A group of enzymes (alpha amylase, beta amylase) present in most malted grains which are responsible for converting starches in the grain into both fermentable and unfermentable sugars. Each enzyme has a specific temperature range in which it is most active. The allgrain brewer steps her mash through a series of temperature rests in order to activate these and other enzymes.

The push required to propel the beer from a keg through a beer dispensing system. The Applied Pressure may be the same as the Ideal Gauge Pressure as in a kegerator beer system or it may be a much higher pressure needed to push the beer through a long draw glycol system. An Applied Pressure higher than the Ideal Gauge Pressure may over pressurize and require properly blended gas in order to avoid changing the flavor and quality of the beer in the keg.

A medium colored specialty malt which has been kilned at temperatures higher than for a pale (base) malt, but lower than for a roasted malt. Sort of like an extra-dark Munich malt. Color is typically around 20L. Contains starch, but probably not enough enzymes to convert itself (should be mashed with pale malt).